FR2618112A1 - ANTI-BLOCKING SYSTEM FOR MOTOR VEHICLE - Google Patents

Abstract

The invention relates to an anti-lock system for a motor vehicle comprising a hydraulic braking system with several circuits. In the system, there is provided an intake valve ensuring the connection of a braking device 14, 17 with the primary chamber 34 of a pressure modulator 21, this intake valve 37 being arranged as a switching solenoid valve. which, in a normal braking operation, that is to say not subject to regulation, occupies its basic position ensuring the connection of the primary chamber 34 of the pressure modulator 21 with the pressure outlet 38 of the device brake 14 while, during the pressure reduction and re-increase phases of the anti-lock regulation system, it is controlled by output signals from the electronic control unit 61 of the ABS system 10 so as to pass in its activation position I where it produces insulation of the primary chamber 34 of the pressure modulator 21 with respect to the pressure outlet 38 of the braking device 14, while, during the duration of the regulation phases where the modulator pressure 21 operates in delivery mode with simultaneous actuation of the brake pressure regulating valves 51 and 52 of the wheel brakes 11 and 12 connected to the pressure modulator 21 in their stop positions, it is returned to its basic position 0 .

Description

The present invention relates to an anti-lock system (ABS) for a

motor vehicle comprising

  a multi-circuit hydraulic fre-ing installation

  baked, which comprises at least one closed braking circuit, which is connected to an outlet pressure chamber of a

  braking apparatus, in which a pressure is

  output voltage proportional to an actuating force

  and can be applied through a

  an intake valve to a primary chamber of a pressure modulator, which comprises a pressure outlet to which is connected a bypass duct, leading to the

  wheel brakes, of the static braking system, which

  carries at least one brake pressure regulating valve

  swimming arranged in the form of a 2/2-way solenoid valve, with the aid of which, for controlling the increase, reduction or pressure keeping phases in the regulation

  anti-lock, the wheel brake (s) subject to the

  may be connected to the exit of the primary chamber

  may be isolated from it, the modula-

  pressure vessel being arranged in the form of a hydraulically actuated piston pump and whose

  drive pressure can be connected via the

  of an ABS function control valve that can be electrically energized, alternatively to the output

  pressure of a hydraulic auxiliary pressure source

  or at its unpressurized storage tank, so that the piston of the pressure modulator, defining the primary chamber with respect to the driving pressure chamber when the inlet valve is open, can be moved under the effect of the pressure biasing of the drive pressure chamber and in opposition to the action of a strong return spring and the pressure in the primary chamber to its limit position associated with a minimum volume of the primary chamber, or when the drive pressure chamber is connected

  the storage tank of the pressure source

  can be transferred under the action of the return spring in its other limit position, associated with a maximum volume of the primary chamber, while in addition the maximum increase or reduction in volume of the

  primary chamber is between 25% and 50% of your

  the amount of brake fluid which can be discharged when the braking apparatus is actuated with the maximum actuation force available in the braking circuit subject to regulation, and furthermore a unit is provided control electronicsABS which produces the necessary control signals for the appropriate control for regulation, ABS control valve and brake pressure control valves from a processing of the output signals, proportional to the speed of wheel rotation and from rotational speed sensors

  which are associated with the wheels of the vehicle.

  Such an anti-blocking system is the subject of the earlier German patent application - and

unpublished - P 36 37 781.3-21.

  In the anti-jamming system described in this patent application, the pressure modulator associated with the closed braking circuit, for example the braking circuit of the front axle, is arranged in the manner of a

  hydraulically operated pump, including the pressure chamber

  discharge pressure - the primary chamber - is delimited in a movable manner by the piston of the modulator relative to

  to the secondary chamber - the training pressure chamber

  ment. The drive pressure chamber can be alternately connected by means of an ABS function control valve, with the high pressure output of an auxiliary pressure source, so that the modulator piston

  repressed, in opposition to the action of a

  powerful pel, in one of its associated limit positions

  at the minimum volume of the primary chamber. In this position

  In the limit position of the piston, an intake valve arranged as a ball-seat valve is held in its opening position by means of a pusher resting on one side against the valve ball and the another side against the piston, so that the outlet pressure chamber of the brake apparatus is in communication with the primary chamber. An output of the primary chamber is connected to both front wheel brakes respectively via a brake pressure regulating valve arranged in the form of a 2/2 solenoid valve.

  tract. In a normal operating condition, is it

  that is not subject to anti-blocking regulation, the

  the high output pressure of the auxiliary pressure source is applied to the drive pressure chamber of the pressure modulator and

  its piston is thus maintained in the limit position as-

  associated with the minimum volume of the primary chamber, the piston and the auxiliary pressure source being dimensioned so that the piston also remains in the aforementioned position when the braking is performed with the maximum brake pressure, which is applied to the wheel brakes through the open intake valve,

  primary chamber and pressure regulating valves

  braking position in their basic positions.

  When there is a tendency to lock on one of the braked wheels, which requires a decrease in the pressure in the wheel brake, the brake pressure regulating valve of the other wheel brake is switched to its position of closure and the control valve-ABS is switched to an activation position in which the control pressure previously applied to the drive pressure chamber of the pressure modulator can be relaxed towards the reservoir.

  pressure-free storage of the pressure source

  iary. Thus, the piston - under the influence of the return spring and the brake pressure applied to the primary chamber - translates in the direction of an increase in volume of the primary chamber so that after a small initial stroke of the piston in this direction, the inlet valve reaches its closed position and, as a result of

  o10 the subsequent increase in volume of the primary chamber

  mayor, a decrease in the pressure exerted on the brake to adjust. The pressure modulator is dimensioned

  so that when

  the maximum possible braking pressure

  applied to wheel brakes and when this pressure

  should be reduced to a large extent by the

  tion, the maximum pressure-reducing stroke for the modulator piston is sufficient in this respect for such a decrease in pressure - within a piston stroke - to be no longer possible, however, when the regulation acts in the necessary direction on both wheel brakes. In such a situation, which can for example be detected by the fact that the output signal, defining the position of the piston, of a position sensor intended to determine the position of the piston, is no longer modified, however the regulation requires in addition, a reduction in the pressure applied to the brakes

  wheels and the brake pressure regulating valves

  Both of the two wheel brakes are switched to their closed position and again the high output pressure of the auxiliary pressure source is applied to the drive pressure chamber of the pressure modulator so that the modulator piston now performs a translation in the direction of a decrease in the volume of its primary chamber, in which case, under the effect of the pressure established in the primary chamber, the intake valve, which is placed in correspondence after a check valve; back, opens and liquid from

  brake is pushed back from the primary chamber into the master-

  cylinder tandem. The pressure modulator works

  in this phase as the discharge pump of the systems

  known anti-blocking systems. After the end of such a "discharge stroke" of the pressure modulator, the pressure reduction mode can be again O10 continued by a new displacement of the piston in the direction of an increase in the volume of the primary chamber, the way explained above. So that the braking system - in the absence of anti-lock control functions - remains able to function correctly when the auxiliary pressure source is deactivated and when the piston of the pressure modulator returns to its limit position corresponding to the maximum volume

  of the primary chamber, a valve for

  also arranged as a ball-seat valve, which opens a second fluid flow path under

  pressure connecting the brake apparatus to the primary chamber

  mayor of the pressure modulator as soon as the piston

  has traveled with respect to the ball of the valve a dis-

  minimum distance of movement corresponding to most of its maximum stroke, the ball having been previously pushed into its closed position by a shutter member biased by spring but which is however driven by the piston from a minimum stroke of the latter so that the ball can open the seat of

  valve. Independently of many functional properties

  advantages of this anti-blocking system by

  compared to anti-lock systems of the same type of con-

  truction corresponding to the prior art, it would be possible to highlight an unfavorable property of this system to the extent o, for example, in the case where the source

  auxiliary pressure has not been "completely"

  tive but only provides a high output pressure

  it is possible that the piston of the modulator can not return, under the effect of a pressure load of its drive pressure chamber, to its limit position corresponding to the minimum volume of the primary chamber, and is also used for the non-regulated braking mode, with the result that the piston moves slightly under the influence of the braking pressure applied to the

  primary chamber, so that the control valve

  admission can also arrive in his posi-

  in a normal braking mode, which leads at least to a limitation of the usable braking pressure and which is of course not permissible.

  An even worse case is natural-

  the output pressure of the source of the output pressure of the auxiliary pressure source is no longer sufficient to bring, in opposition to the restoring force of the return spring - powerful - at least to near its limit position associated with the minimum volume of the primary chamber, so that the ball of the intake valve is spaced from its seat at least a distance corresponding to a part of its normal opening stroke while the bypass valve remains in its closed position by the translational movement, in part possible, of the piston of the modulator. In this case, it is practically impossible to brake with the brake circuit connected to the pressure modulator. Another disadvantage obviously less important also relates to the structure

  relatively complicated mechanics of the modulator of pres-

  including the inlet valve and the

derivation.

  An object of the invention is therefore to improve an anti-lock system of the type defined above, so that, with a simplified structure, it is less prone to failures and that is particularly ensured that the installation braking system maintains its correct operating condition in case of

  failure of the auxiliary pressure source.

  This problem is resolved in accordance with the

  in that the inlet valve is provided under

  me of a switching solenoid valve which, in a

  braking ration, that is to say, not subject to the

  regulation, occupies its basic position ensuring the link between

  sound of the primary chamber of the pressure modulator with the pressure output of the braking apparatus while, during the duration of the decreasing and re-increasing phases of pressure during the regulation

  anti-blocking, it is controlled by signals from

  electronic control unit of the ABS system so as to move to its activation position

  produces insulation of the primary chamber of the modula-

  pressure of the pressure apparatus of the braking apparatus, while during the duration of the control phases o the pressure modulator operates in the discharge mode with simultaneous excitations of the brake pressure control valves of the brake brakes. wheels connected to the pressure modulator into their stop positions, it is returned to its basic position. Due to the arrangement provided here of the intake control valve in the form of a solenoid valve, this can be controlled independently

  the instantaneous position of the modulator piston, respec-

  Finally, it is ensured that in any possible position of the piston it is possible to perform braking. The increase in technical complexity resulting from the fact of using a solenoid valve is counterbalanced by a significant simplification of the structure of the pressure modulator because one removes on the one hand a mechanical admission valve and a mechanical bypass valve as well as the control organs. actuation or closing necessary for their control and thus the pressure modulator can be manufactured in a much cheaper way and also

  with smaller spatial dimensions.

  According to another feature of the invention

  tion, a position sensor is provided which produces

  electrical output signals characterizing the posi-

  of the pressure regulator piston, these signals being applied as further information inputs to the ABS control electronics, and the intake control valve is returned within a control cycle anti-blocking device having, where appropriate, several phases of reducing, maintaining and re-increasing the pressure, in its basic position when the ABS function control valve is switched to its basic position, all the brake pressure regulating valves of the braking circuit subjected to the regulation occupying their stop positions and the output signal of the position sensor indicating that the piston of the modulator has moved to its limit position corresponding to a minimum volume of the primary chamber. This provides an advantageous arrangement of the anti-lock system according to the invention, where it is possible, using simple logic combinations,

  to control the solenoid valve according to a sequence

  quence and with a duration in accordance with the regulation.

  According to yet another particularity of the invention, the intake valve, after it has been controlled during an anti-lock regulation phase to go into its stop position, is also brought back to its position. when, during regulation, the slowing of the vehicle - which can be detected by the variation of the output signals of the wheel speed sensors -

  decreases below a predetermined threshold value.

  Thus, the pressure in the primary chamber is adapted as quickly as possible to the pressure of

  driver-produced command by means of the

  braking force, as well in the direction of a climb

  braking pressure only in the sense of a reduction in

nution of the pressure.

  According to yet another particularity of the invention, the wheel brake or brakes which are subjected to the anti-lock regulation can be connected, via a non-return valve, to a bypass duct leading to the exit pressure of the braking apparatus; so when the driver

  "release" the brake pedal during a control phase

  lation, the braking pressure can be rapidly reduced. According to yet another particularity of the invention, the circulation passage of the valvedecommand-ABS which ensures, in the basic position of this valve, the

  connection of the pressure output of the pressure source

  auxiliary pressure with the pressure chamber of

  of the pressure modulator, is provided with a

  limiting the flow velocity of the pressure medium to the modulator to a predetermined value;

  so with very simple technical means, we ob-

  holds the possibility of establishing an optimal relationship between the rates of variation of the brake pressure in the phases of decrease and pressure rise of the

anti-blocking regulation.

  According to yet another particularity of

2 6 1 8 1 1 2

  According to the invention, there is provided another function control valve which can be controlled by output signals from the control electronics, so that in the base position of the valve a pressure accumulator can be filled. by a pump of char-

  which is maintained at a pressure level of

  determined, necessary for the source of pressure

  liar, which is controlled by the opening pressure of a pressure limiting valve, connected between the pressure outlet, the pump and the return duct leading to the storage tank, is connected, via the valve anti-return output of the auxiliary pressure source, at its pressure output when the high pressure output of the pump is however isolated from the return pipe, and that in the first

  activation position of this valve, the accumula-

  The pressure transmitter is isolated from the pressure output of the auxiliary pressure source and, however, the pressure output of the pump is connected to the return line of the auxiliary pressure source. Thus, it is possible by means of another function control valve associated with the auxiliary pressure source

  to order, in a simple way, phases of

  pressure of anti-blocking and simul-

  temporarily filling a pressure accumulator

  provided in association with the pressure source

  and, by means of this valve, it is also possible to obtain a less severe operating mode of the battery filling pump by a short-circuiting of the pressure limiting valve, whose opening pressure determine the

  level of pressure in the accumulator.

  According to yet another particularity of the invention, the pressure modulator is arranged in the form of a stepped profiled air cylinder comprising stages

  boring, joining each other by the interme-

  of a casing shoulder, and in addition a corresponding staggered profile piston, the large diameter stage of which constitutes the moving limit of the drive pressure chamber and whose small diameter stage

  constitutes the mobile limit of the primary chamber of the

  pressure regulator; and the piston has, between its flange-like zones sealingly applied

  against the corresponding boring stage, a central part

  trale reducing section in an axial direction and having a conical outer circumferential surface

  against which a stem of action

  position sensor, which includes a

  stroke / tension weaving device by means of which radial displacements, combined with axial movements of the piston, of the actuating rod are converted into voltage signals which can be processed by means of the electronic control unit of the ABS system. This gives simple arrangements of the modulator piston and a

  piston position sensor which allows a determination of

  precise position of the momentary position of the piston

as its speed of movement.

  According to yet another particularity of the invention, the return spring, pushing the modulator piston in its limit position associated with the volume

  maximum of the primary chamber, presents laforne d'unres-

  a compression coil, which is received over a portion of its length corresponding to the axial dimension of the small piston stage, including the conical central portion of the piston, in a central blind hole of the modulator piston. In this way, this return spring still exerts, also in the limit position of its piston, which is associated with the maximum volume of the primary chamber of the depressor modulator, a force of

  desired recall before compression.

  According to still other features of the anti-lock system according to the invention: the piston of the modulator can be supported by means of an additional return spring against the housing of the pressure modulator, the restoring force of this spring reaching its maximum in the position of the piston which corresponds to the minimum volume of the primary chamber and decreasing to the value 0 as

  the piston moves away from this limit position,

  within an interval h of between approximately 1/4 and

  1/8 of the total stroke H of the piston.

  - The sum of the maximum values of the

  these recall the return springs and the force that is the result of the solicitation of the small piston stage by the maximum output pressure of the braking apparatus, which are directed in the direction of an increase in the volume of the primary chamber, is maximum and is approximately equal to the force which, during a biasing of the modulator piston by the output pressure of the auxiliary pressure source, forces the piston back to its limit position associated with the

  minimum volume of the primary chamber.

  This gives the output signal

  position sensor, each time in an ex-

  its pressure increase stroke reaches a value corresponding to the pressure prevailing in the drive pressure chamber so that, for example, its rise speed can be used for a control of the operation of the pressure source.

auxiliary.

  According to yet another feature of the invention, the other call spring has the shape of an annular spring, which is supported on one side against

  the shoulder of the pressure modulator housing.

  According to yet another particularity of the invention, for each brake wheel of the braking element which can be subjected to regulation, it is

  a pressure modulator, a pressure relief valve

  a brake control valve and an ABS control valve. It is thus possible to

  to kill a regulation in "phase opposition", that is,

  say that the brake pressure applied to a brake

  the wheel is increased while the brake pressure

  swimming applied to the other wheel brake is reduced.

  Additional security of function

  the anti-lock system and the braking system as a whole can also be achieved by providing another planned and arranged solenoid

as a bypass valve.

  According to still other features of the anti-lock system according to the invention: the piston of the modulator is provided with a

  electronic pressure sensor, which produces at its

  an electrical signal representing the pressure

  prevailing in the primary chamber of the pressure modulator.

  - The piston of the modulator comprises a

  forming the large diameter stage and a strong part

  the small diameter stage, which is displaceable by translation relative to the other part, and in that the pressure sensor comprises a sensing element held between the two aforementioned parts of the piston and which can be biased in compression or in deformation under the effect of the pressurization of one of the parts of the piston under the action of the pressure in the primary chamber of the pressure modulator, producing

  thus at its output a corresponding electrical signal.

  - The capture element is arranged under the

  form of an electrical resistance sensitive to a compres-

  sion or a distortion or in the form of a

piezoelectric element.

  Other features and advantages of the invention will be highlighted, in the following

  description, given by way of non-limiting example, in

  reference to the accompanying drawings in which: Figure 1 represents, in the main

  for the braking circuit of the front axle of a vehicle

  vehicle, an anti-lock pattern in accordance with the

  vention, comprising only a pressure modulator

  provided for the regulation of the applied brake pressure

  the two wheel brakes of this braking circuit

swim;

  Figure 2 gives a representation, cor-

  corresponding to that of Figure 1, an example of a

  where pressure modulators are associated with

  respectively to the wheel brakes that may be subject to regulation; 3 schematically represents an anti-lock system (ABS) corresponding in its basic structure to the ABS system of FIG.

  a pressure modulator provided with an inlet valve

  and an electrically controllable bypass valve, and Figure 4 shows a special arrangement

  a pressure modulator that can be used in combination

  pairing with the anti-blocking systems of Figures 1 to 3.

  In Figure 1, whose features

  will be described expressly, the following

  essential for its operation, an anti-lock system arranged in accordance with the invention, generally designated by 10 and usable in a vehicle

  car having a hydraulic braking system

  two-circuit hydraulics, the front wheel brakes 11 and 12 of which are connected to a front axle brake system I and whose rear wheel brakes, not shown for convenience, are connected to a

  rear axle braking circuit II, which is

  shown in Figure 1 simply by its brake line.

  main course 13 diverging towards the wheel brakes

  back. Both braking circuits I and II are sup-

  posed to be static braking circuits. As

  braking apparatus, in the example of a special embodiment shown in FIG.

  tandem cylinder 14 of a conventional construction, which can be actuated via a brake force amplifier 16, for example a vacuum braking force amplifier, by means of the brake pedal 17. The circuit front axle braking I

  is connected, as is conventional, to the primary chamber

  output pressure port 18 of the tandem master cylinder 14, while the rear axle brake circuit II is connected to the secondary outlet pressure chamber

19 of this tandem master cylinder 14.

  Without limiting the generalities, we will

  ask that the anti-lock system is performed as well

  for the front axle as for the rear axle of the vehicle

  according to the same principles of construction so that it is sufficient to give details of construction and operation of the anti-lock system only in relation to the front axle. In this respect, it is obvious that the anti-lock system provided on the rear axle could also be produced according to another principle known per se, for example the principle of displacement. As regards the literary indices which

  will be used in the following description and / or

  the figures of the drawings, the index "V" will designate the front axle, the index "H" the rear axle, the index "L" the left side of the vehicle and the index "R" the right side of the vehicle. In the special embodiment shown in FIG. 1, it is intended as an element

  central functional part of the functional part of the

  anti-lock system 10 acting on the axle before a

  pressure regulator generally designated 21 and by means of which it is possible to control phases of increase and reduction of the brake pressure during an anti-lock control cycle taking place for one or the other other wheel strands 11 and / or 12 of the front axle brake circuit I. The pressure modulator 21 is arranged as a stepped profile cylinder, the housing 22 of which has two stages of bore 26 and 27, separated Mon

  on the other by a radial shoulder 23 and which are dis-

  placed coaxially with respect to the central longitudinal axis of the housing 22 of the modulator, a piston of this modulator, of corresponding stepped profile and generally designated by 28, sealingly applying against the stages of the bore by the intermediate of an annular seal 29 or 31 integral with the

piston.

  By means of flange 32 of small diameter

  of the piston 28 of the modulator, it is created in the modula-

  The pressure chamber 21 is a functional chamber, hereinafter referred to as the primary chamber 34, which is movable within the small bore stage 26 and which is delimited by an end face wall 33 which closes outwardly this stage. bore 26; this primary chamber 34 comprises a pressure inlet 36 which is connected, via a control valve 37, arranged in the special embodiment shown in the form of a 2/2-way solenoid valve, to the primary pressure outlet 38, associated with the front axle braking circuit I, of the tandem master cylinder 14, and a pressure outlet 39, to which is connected the main braking line 41 of the braking circuit

1 7 2618112

  front axle I, diverging towards the wheel brakes 11 and 12. The ring-shaped large diameter stage 42 of the piston 28 of the modulator, as well as the end end wall 43 of the modulator housing 22, assuring the closing towards the outside of the housing bore 27, against which the large diameter stage 42 of the modulator piston is sealingly applied, delimit

  in an axial direction a pressure chamber of

  flow train 44, which can be connected via an ABS control valve 46 alternately to an outlet 47, maintained at a high pressure level, of a hydraulic auxiliary pressure source generally designated 48, or well that can be relaxed by

  compared to its supply tank - without pressure -

41.

  The control valve-ABS 46 is arranged in the form of a 3/2-way solenoid valve which ensures, in its base position 0, the connection of the drive pressure chamber 44 of the pressure modulator 21 with the output pressure 47 of the auxiliary pressure source 48, but which is however isolated from its storage tank 49 while, in its activation position I, it provides the connection of the drive pressure chamber 44 of the pressure modulator 21

  with the storage tank 49 of the source of pres-

  auxiliary circuit 48, while being isolated from its

pressure 47.

  The brake pressure regulating valves 51 and 52, with which the braking line branches 41 'and 41 "of the braking circuit

  front axle I may be closed for the purpose of

  the phases of reduction, maintenance and increase

  pressure regulation of the anti-blocking

  or - temporarily - together in the direction of the pressure output 39 of the pressure modulator 21, are arranged as 2/2-way solenoid valves, the basic position of which is the open position, while

* whose activation position is the closed position

shutdown.

  In addition, the wheel brakes 11 and 12 are respectively connected via a check valve 53 or 54 with a bypass duct 56,

  which is itself directly connected to the output of pres-

  primary bearing 38 of the tandem master cylinder 14 or to a brake line portion 41 "'of the front axle braking circuit I, resulting in the

  command 37, by means of which this output of pres-

  primary 38 can be isolated from the pres-

  sion 36 of the pressure modulator 21.

  The check valves 53 and 54 are solenoid

  lawful in the opening direction by a pressure which is stronger in the cylinders of the front wheel brakes 11 and 12 than in the bypass duct

  56 or in the primary pressure chamber 18 of the master

  tandem cylinder 14, so that if the intake control valve 37 were to remain in its position

  closing pressure, the brake pressure can be adjusted

  through the bypass duct 56 when the driver releases the force exerted on the

brake pedal.

  The piston 28 of the modulator is provided with a central blind hole 57, whose depth, measured in

  the direction of the central longitudinal axis 24, corresponding to

  it is approximately equal to the length of the small diameter stage 32 of the piston, this blind hole 57 being open towards the primary chamber 34 of the pressure modulator 21. A "powerful" return spring 59 is supported on one side against the bottom 58 of this blind hole 57 and the other side against the end end wall 33, which closes out the small bore stage 26, this return spring having a tendency to push back the piston

  modulator 28 of the position shown, which corresponds to

  approximately at the limit position of the piston 28 which is associated with the minimum volume of the primary chamber 34, to its other limit position, which is associated with the maximum volume of the primary chamber 34 or

  the minimum volume of the drive pressure chamber

  44, the modulator piston 28 bearing, in this limit position shown on the left in FIG.

  against the extreme end wall 43 of the modula-

  22, which closes the large floor to the outside

Bore 27.

  Before describing in the following other parts

  the constructional features of the pressure modulator 21 and its function, it will initially be specified how the necessary phases of increase, maintenance and reduction of pressure can be controlled by means of the functional components of the ABS system 10 for the

  front wheel brakes 11 and 12 during anti-lock

blocking.

  As long as the anti-regulation system

  blocking is not required, the intake control valve 37, the ABS control valve 46 and the brake pressure control valves 51 and 52 occupy their basic positions shown. The piston 28 of the pressure modulator 21 is biased, on its surface F1 corresponding to the sectional area of its stage.

  large diameter 42, by the outlet pressure - high -

  PA of the auxiliary pressure source 48, which is applied

  to the drive pressure chamber 44 of the

  pressure valve 21 via the valve of

  ABS-control 46 in its basic position 0.

  On its surface F2, corresponding to the section surface of the small piston stage 32, the piston 28 of the modulator is biased by the braking pressure PB 'produced by means of the braking apparatus 14 and applied to the primary chamber 34 by via the intake control valve 37 being in its basic position 0, this braking pressure being also transmitted to the wheel brakes 11 and 12

  of the front axle braking system I through

  of the brake pressure regulating valves 51 and 52 which are connected to the pressure outlet 39 of the

modulator 21.

  The ratio F1 / F2 of the active surfaces of the piston 28 of the modulator is chosen to be sufficiently large for the piston 28, also when the maximum braking pressure PB can be obtained in the primary chamber 34 by actuating the

  braking 14 is applied, either pushed by the request

  pressure of its large floor 42 with the pressure

  PA output voltage of the auxiliary pressure source 48

  - in opposition to the increasing force of

  reminder 59 - to its right limit position, in Figure 1, associated with the minimum volume of the primary chamber 34 and can be maintained in this position and remain as long as the control pressure chamber 44 is connected to the high pressure output 47 from

the auxiliary pressure source.

  When a blocking tendency occurs during braking, for example for the left front wheel, in this case a necessary phase of pressure decrease is obtained by the antilocking control system in that the control 37, -30 connected between the pressure output 38 of the brake apparatus 14 and the pressure input 36 of the pressure modulator 21, is switched to its activation position I - the closed position -, while the ABS control valve 46 is also switched to its activation position; the open position allowing the connection of the driving pressure chamber 44 with the unpressurized storage tank of the auxiliary pressure source 48, and that the brake pressure regulating valve 52 of the right front wheel brake 12 is also switched to its activation position I

  - the closed position - while the control valve

  brake pressure 51 which is associated with the wheel brake 11 in which the braking pressure is to

  to be diminished remains in its basic position O - the posi-

opening.

  The pressure decrease thus occurs so that the piston 28 of the modulator, because of

  the pressure discharge of the pressure chamber of

  44, is now moved by the jurisdiction of

  recall and by the pressure prevailing in the primary chamber

  mayor 34 in the sense of an increase in volume of the

  primary chamber 34 so that the brake fluid pro-

  from the wheel brake 11 can flow into the primary chamber 34 of the pressure modulator 21. Pressure reduction phases in the right wheel brake or in both front wheel brakes 11

  and 12 can proceed in a similar way.

  When, after a phase of pressure decrease, the brake pressure in the brake

  of wheels which are subject to regulation must be

  continued, while the control valve 37 remains in its closed position, a switching of the two brake pressure regulating valves 51 and 52 in their closed positions I, while the control valve-ABS 46 is again brought back to its basic position O, so that it settles in the

  drive pressure chamber 44 again the pres-

  PA output voltage of the auxiliary pressure source 48

  but that it can not, however, occur

  piston 28 in the direction of increasing the

22 * 2618112

  brake pressure because the primary chamber 34 of the

  The pressure washer 21 is insulated both with respect to the tandem master cylinder 14 and with respect to the brakes

of wheels 11 and 12.

  In order to carry out a pressure increase phase which is then required, the brake pressure regulating valve 51 and / or 52 of the corresponding wheel brake 11 and / or 12 is returned to the position base 0 while the control valve 37 connected upstream of the pressure inlet 36 of the pressure modulator 21 is still held in its closed position I. Under the influence of the outlet pressure PA of the pressure source auxiliary 48, which is applied to the drive pressure chamber 44 of the modulator

  pressure 21, the piston 28 of the modulator moves

  holding in the direction of a decrease in his primary chamber

  34 so that brake fluid, which had been au-

  received by the primary chamber 34 from the

  or wheel brakes 11 and / or 12 subjected to the

  in the direction of a decrease in pressure, is now again returned back to the wheel brake or brakes 11 and / or 12 in the direction of a rise in pressure. When, after a pressure increase phase controlled in this manner by the anti-lock control system, there is no longer a tendency to block in the front axle, the control valve 37, connected "between" the master-cylinderretandem 14 and the pressure modulator 21 is again brought back to its basic position 0 so that, for another rise in the brake pressure, the outlet pressure

  PB of Tandem Master Cylinder 14 is available again.

  The activation signals necessary for the control of operation, correct for regulation, of the control valves 37 and 46 as well as the brake pressure regulating valves 51 and 52 are produced,

  according to known criteria, by an electronic unit

  ABS control unit 61, shown schematically

  Figure 1, essentially by means of a

  comparing and differentiating the output signals of the sensors 62 and 63 of the wheel rotation speeds, which are provided to control the motion behavior of the vehicle wheels and which produce at their outputs electrical signals characterizing the

peripheral wheel speeds.

  In the ABS system 10 of Figure 1, it is possible to obtain different control phases in the two front wheel brakes 11 and 12 as far as in one of the wheel brakes. 1 or 12, the brake pressure can be maintained while it is lowered or increased in the other front wheel brake 12 or 11. It is not possible to obtain a "in opposition of phase" variation of the brake pressure in both front wheel brakes 11 and 12 ", ie an increase of the brake pressure in one of the brakes 11 or 12 while simultaneously the brake pressure in the other wheel brake 12 or 11 is simultaneously decreased, however, such a "counter-phase" braking pressure regulation in the front wheel brakes 11 and 12 can be realized in the exemplary embodiment shown in FIG. described in detail, in that in each of the branches of the front axle braking circuit,

  from the point of junction 64 of the braking circuit

  front axle and which are designated in their

  appears by 66 and 67, a modulator of pres-

  21 of a structure as described with the aid of Figure 1, a link control valve 37 and a control valve ABS 46 of the type already described, these components being associated respectively with one of the two brakes of front wheels 11 and 12, while the source of

  auxiliary pressure 48 can be used, with the bran-

  hydraulic system shown in Figure 2, for

  two branches 66 and 67 of the braking circuit.

  The arrangement of the electronic control unit 61 'of the ABS system 10' of Figure 2, which is necessary to provide the possibility of a control

  "in opposite phase" of a brake pressure applied

  front wheel brakes 11 and 12, should be referred to a specialist in the field of

  so that it seems superfluous to give further explanations

cations in this regard.

  Provided that, in addition, the functional elements shown in Figure 2 are filled

  same numerical references as elements corresponding to

  of Figure 1, the corresponding parts of

  the description in Figure 1 will not be repeated,

  the same consideration also applies to

  structural and functional elements represented on the

  Figure 1 and which will be mentioned later.

  Figure 3, to which reference will be made in detail, represents another embodiment of a

  10 "anti-blocking system within the framework of the

  The invention is substantially similar in function to that shown in FIG. 1, while differing therefrom by the special arrangement of the pressure modulator 21 'in connection with the pressure admission valve 37'. arranged here as a mechanical valve and which ensures the transmission of

  pressure of the braking apparatus 14 to the primary chamber

  mayor 34 of the pressure modulator 21 ', and further by

  the fact that a bypass valve is

  68, arranged in the form of a 2/2 way solenoid valve electrically energizable and by means of which the output pressure of the tandem master cylinder 14 can also be applied to the wheel brakes 11 and 12 of the brake circuit. front axle braking I when the intake valve 37 'must reach its closed position as a result of erroneous operation, and also by the fact that an additional functional control valve 69 is provided by means of from which it is possible, among other things, to order in combination

  with the control valve-ABS 46 the pressure supply

  control voltage of the drive pressure chamber

44 of the pressure modulator 21 '.

  Provided that the structural and functional elements of the ABS system 10 "of Figure 3 are provided with the same numerical references as

  of the ABS system 10 in Figure 1, reference is made to

  of the description in Figure I which corresponds to them

  tooth, to avoid repetitions. The description of

  the embodiment of Figure 3 will therefore be

  limited to the structural and functional elements which differentiate it from the example of

Figure 1.

  The pressure-admission valve 37 'is arranged, in the illustrated special embodiment, in the form of a ball-seat valve, the seat of which

  71 is constituted by a conical chamfer of the channel of

  pressure beam 36, this chamfer being located on the outer side of the end end wall 33, delimiting the primary chamber 34 in an axial direction, the housing

  22 of the modulator, and its ball 72 is constantly solicited

  by a prestressed spring 73 which produces a force tending to push the ball 72 into the position of

  closing the intake valve 37 '.

  The intake valve 37 'has a pot-shaped body 74, pressure-tightly mounted on the outer side of the end end wall 33 of the pressure modulator housing 22 and defining a valve chamber 76 which is in communication - in

  the open position of the intake valve 37 '-

  with the primary chamber 34 of the pressure modulator 21 'and which is provided with a pressure inlet 77, connected via the portion 41 "' of the main braking line of the front axle braking circuit I

  at the pressure input 38, associated with it, the master

  tandem cylinder 14, as well as a pressure outlet 78 from which the bypass flow path 79 which - bypassing the ball valve seat 37 '- leads to the output 39 of the pressure modulator 21' or the main braking line 41, connected thereto, of the front axle braking circuit I. In the basic position 0 of the bypass valve 68, this bypass flow path 79 is open while in the activation position I of

  the bypass valve 68, this channel is closed.

  The piston 28 of the pressure modulator 21 'is provided with a slender central pusher 81, in the form of an elongate rod, which penetrates at its free end, into

  the basic position represented by the piston 28 of the modula-

  tor, which is taken as long as the ABS system 10 "is not activated, in the pressure inlet channel 36 connecting the primary chamber 34 of the pressure modulator 21 'with the valve chamber 76 thus maintaining the ball 72

  the valve removed from its seat 71 - the position of

opening of the valve 37 '.

  When the inlet valve 37 'reaches, for example, under the effect of a failure of the auxiliary pressure source 48, in its closed position, there then occurs braking of the front axle via of bypass flow path 79

  open in the basic position 0 of the diverter valve

68.

  The functional control valve 69, provided

  additionally in association with the source of pres-

  auxiliary circuit 48, is arranged in the exemplary embodiment

  The special illustration shown, like a 2/4 way solenoid valve, is connected firstly "between" a pressure accumulator 82 of the auxiliary pressure source 48 and

  its exit 47 and on the other hand "between" the high pres-

  83 of an accumulator filling pump 84

  view for filling the pressure accumulator 82 and the storage tank - without pressure - 86 of the

auxiliary pressure source 48.

  In the basic position 0 of this functional control valve 69, the pressure accumulator 82 is connected via a passage 87 of the

  functional control valve 69 and the check valve

  output return 88 at the pressure output 47 of the auxiliary pressure source 48 while the pressure output 83 of the filling pump 84 of the accumulator is isolated from a return line 88 leading to the storage tank 86 and through which, in the activation position I of the ABS control valve 46,

  fluid under pressure from the pressure chamber

  the drive train 44 of the pressure modulator 21 'can

  return to the storage tank 86 of the source of pres-

auxiliary action.

  In the activation position I of the valve

  functional control unit 69 of the pressure source

  48, its pressure accumulator 82 is isolated from the pressure outlet 47. Because now the output

  pressure 83 of the pump 84 for feeding the accumula-

  The driver is then connected, via a passage 91 of the control valve 69, to the return duct 89 or

  to the storage tank 86 of the pressure source

  48, it occurs in this functional position

  I of the valve 69, a short-circuiting of the limiting valve

  pressure 92, connected on the one hand between the storage tank 86 or the return duct 89 and, on the other hand, the pressure outlet 83 of the pump 84

  supply of the accumulator, by way of

  Bypass portion leading to the passage 91 of the functional control valve 69, which provides the advantage that when the pump 84 is to operate in the

  circulation, that is to say when this pump 84 is ac-

  but when the accumulator 82 does not

  not be filled, this pump must not operate oppo-

  at the opening pressure, determining the maximum accumulator pressure, the

pressure 92.

  By switching the control valve

  In its operative position II, it is possible to interrupt a pressure increase phase of the anti-lock control system during which the piston 28 of the pressure modulator 21 'moves in the direction of a reduction of its primary chamber 34, that is to say that the piston 28 of the modulator is "stopped" in a position situated between its positions

possible limits.

  The functional control valve 69

  also an element of the ABS 10 "system which is es-

  sensel to fulfill its function. In order for the aforementioned function in the embodiment of FIG. 1 to be filled, it is necessary that, while the admission control valve 37 is already in its closed position I, the two braking pressure regulating valves 51 and 52 are simultaneously switched in their closed positions I. The modification, necessary in the embodiment of Figure 3, of the electronic control unit 61 ", which produces the appropriate activation signals for the control, correct for regulation, the control valve-ABS 46, the bypass valve 68, the functional control valve 69 and the brake pressure regulating valves 51 and 52,

  the possibilities of a knowledgeable specialist

  the field of regulation, so that it is not necessary to give further explanations to

this regard.

  For the description of other particular

  of construction and operation that are provided in each of the exemplary embodiments, we will

  again, for simplicity, refer to Figure 1.

  The pressure modulator 21 is provided with a distance or position sensor 92, which produces an output signal typically defining the corresponding position of the piston, varying constantly during the movements of the piston 28 of the modulator and which is applied under the form of an additional input information to the electronic control unit 61 of the ABS system 11. This distance sensor 92, which can be arranged in a known manner in the form of a sensor

  resistance or inductive sensor, captures in the example

  special realization represented the position, va-

  in a radial direction, an action rod

  93 which is supported by its free end against a conical peripheral surface 94 of the piston 28 of the modulator, which is located between the flanges 32 and 42 of the small stage and the large stage of the piston 28 of the modulator, sealingly pressing against the surfaces of the. small stage 26 and large stage 27 of the bore of the modulator, said surface 94 decreasing in section towards the

  large stage42 of the piston, as shown in Figure 1.

  The axial dimenson and the disposition of this conical peripheral surface 94 are designed such that the output signal of the position sensor 92 is in net correlation with the position of the piston in each of the intermediate positions.

  that it can take between the two limit positions.

  Advantageously, the position sensor is moreover

  arranged in such a way that its output signal varies

  in proportion to the variations of position of the piston.

  The output signal of this position sensor 94 can also be used for function control and function control of the ABS system 10, such as

this will be specified later.

  In addition to the spring 59

  In the entire stroke range H, there is provided a second return spring 96, which produces a restoring force only in a small fraction h = H / 4 - H / 6 of the total stroke. The second return spring 96 is arranged, in the special embodiment shown, in the form of an annular spring through which the piston 28 of the modulator can be supported by its large stage 42 against the shoulder 23 housing, which separates the large bore 27 of the small bore 26 of the housing 22 of the modulator. This second return spring 96 produces its maximum restoring force in the limit position of the modulator piston which is associated with the minimum volume

  of the primary chamber 34 and he does not intervene, too-

  early that the piston 28 of the modulator is moved away from this limit position of the stroke fraction h or more in the direction of an orientation of the volume of the primary chamber, in the generation of the restoring force acting on the

piston 28.

  This return spring 96 is dimensioned

  so that the sum of the restoring forces -

  respectively - which are produced by the

  59 and the return spring 96 in the position

  piston limit 28 which is associated with the minimum volume

  primary chamber 34, which is less than a small fraction, for example 5% to 10%, to the force acting on the piston 28 when its drive pressure chamber

  44 is solicited by the maximum outlet pressure of -

  the auxiliary pressure source 48. With this arrangement of the return springs 59 and 96, the output signal of the position sensor 92 can be used, in a control cycle in which the braking installation is

  not operated but o the pressure chamber causes

  However, 44 is called upon by the pressure of

  of the auxiliary pressure source 48, to verify

  the reliability of the auxiliary pressure source 48.

  Unlike the representation of FIG. 1 which is not drawn with a unit scale, the braking apparatus 14 and the pressure modulator 21 are dimensioned such that the increase in volume V that the primary chamber undergoes 43 when the piston

  28 of the modulator is brought back from its corresponding limit

  laying to the minimum volume of the primary chamber 34 to its limit position corresponding to the maximum volume of this primary chamber 34, much smaller than the volume VBmax of the amount of brake fluid which, when the device is actuated 14 with the maximum possible force that can be exerted on the pedal, can be discharged from the primary outlet pressure chamber 18 of the braking apparatus 14 into the braking system of the front axle I. An advantageous dimensional relationship in this respect is defined as follows: 0.25 V / VBmax - 0.5 (1) and preferably by the following formula: V / VBmax = 1/3 (2) This dimensioning of the pressure modulator 21 has the consequence that the decrease in pressure

  obtained when requesting the regulatory system.

  anti-blocking by a single stroke of the piston of the

  pressure limiter 21 in the brake (s) 11 and / or 12

32 2618112

  subject to regulation is no longer sufficient in each

  case to stop the tendency to block.

  Such a braking situation is

  for example, when braking has been initiated on a road zone with a high coefficient of friction, and consequently of force transmission, between the road and the vehicle wheels, so that the actuating force - and therefore also the brake pressure - was increased practically to the corresponding maximum value, and when the vehicle subsequently arrived on a road zone with a very high

  low coefficient of friction, that is to say of

  mission of force, for example of 0.3, between the road and the tires. The wheels of the vehicle which are very strongly braked in this case tend to go into

  match "quickly" in a blocking condition.

  The regulatory system reacts and, in such a situation,

  a large amount of brake fluid must be

  to be relieved of the wheel brakes to

  braking pressure required to stop the blocking tendency. When for this purpose the piston of the modulator reaches its limit position associated with the maximum volume of the primary chamber 34, or at least in the immediate vicinity thereof, which is detected by the electronic control unit 61 of the system ABS 10 from the output signal of the position sensor, while simultaneously the tendency to blocking is stopped, which is detected by the electronic control unit from the processing of the output signals of the wheel speed sensors , on the one hand, a switching of the brake pressure regulating valves 51 and 52 into their closed positions I and a return of the control valve ABS 46 and the intake control valve 37 in their basic positions 0, with the result that now brake fluid, which had previously been received by the primary chamber from the brake wheel (s) 11 and / or 12 subject to regulation, e This is caused by the displacement of the piston 28 of the modulator as a result of the pressure loading of the entrainment pressure chamber 44, in the direction of a decrease in the volume.

  from the primary chamber to the pressure chamber of

  of the master cylinder-tandem 14. The

  In this anti-lock control phase, the pressure sensor 21 operates as a delivery pump in such a way that, because brake fluid has been pumped back into the tandem master cylinder, also

  it is possible to feel at the brake pedal the ac-

  tivation of anti-blocking regulation. At the latest then, when the piston 28 of the modulator has reached its limit position associated with the minimum volume of the primary chamber 34, which is again detected by the output signal of the piston position sensor 92, there is a switching of the pressure modulator 21 of

  "repression mode" in the pressure decrease mode

  such that the brake regulating valve (s) 51 and / or 52, corresponding to the wheel brake (s) 11 and / or 12, in which the brake pressure is to be decreased again, is or are returned to the position base 0, while the intake control valve 37 is again switched to its closed position I and the control valve-ABS is at

  switched to the activation position I produced

  the pressure drop in the pressure chamber

drive.

* Decrease in brake pressure,

  In this case, within the possible travel H of the piston 28 of the pressure modulator, and manifesting itself in the wheel brake (s) 11 and / or 12 subjected to the regulation, it will generally be sufficient to

  stave off a tendency to blockage which has manifested itself

  for the corresponding wheels of the vehicle.

  The flow passage 98, through

  the accumulator 82 of the source of pres-

  auxiliary voltage 48 is connected in the basic position 0

  of the ABS control valve 46, with the pressure chamber

  of the pressure modulator 21, is provided with a throttle 99 by means of which, in the

  pressure increase phases of the anti-

  blocking, which are controlled by displacement of the modulator piston 28 in the direction of a decrease in the volume of the primary chamber 34 of the pressure modulator 21,

  there is an increase in the speed of increase

  tion of the pressure in the primary chamber 34, i.e.

  say of the time increase of the output pressure of the pressure modulator 21. The resistance to flow

  opposed by this constriction 99 is advantageously chosen

  so that a "rate of change" of the pressure modulator output pressure can be obtained which is large enough to achieve a control sensitivity while the speed at which the piston 28 moves in a phase of increase of

  However, the pressure of the anti-blocking

  weakly so that its position is captured with good accuracy by the sensor 92 which can be used, in the sense of optimal control of the phases

  increase, maintenance and, where appropriate, reduction

  pressure by the anti-tamper

  blocking. By correctly operating the output signal of the position sensor 92, it is thus possible to achieve a pressure adjustment, which is correct for regulation, in the successive pressure increase phases during a control cycle in which the anti-lock regulation system, whose effectiveness is

thus globally increased.

  In this respect, an advantageous mode of

  the pressure increase phases, of which the

  technical realization in the form of an electronic control

  tronic comes within the framework of the knowledge of an average specialist in the field of regulation, is for example the following

  When the increase phase of

  sion starts in a position of the piston 28 of the modula-

  which corresponds to the maximum volume of the primary chamber

  mayor 34 of this modulator 21, which is detected by the electronic control unit 61 from the output signal of the position sensor 92, the control unit 61 "analyzes" this as an indication that the previous phase or phases pressure decreases have produced a significant decrease in pressure so that the vehicle can move on a "bad" ground, i.e. with a low coefficient of friction with respect to the vehicle wheels. In this case, the phase

  pressure increase is then interrupted before

  by a pressure maintaining phase, after the piston 28 has made a displacement producing

  an increase in pressure, this displacement cor-

  laying at about halfway its maximum H.

  In this respect, a check is made with the help of

  output gears of the rotational speed sensors of the wheels to determine whether the brake slip of the wheels subject to regulation continues to increase or continues to decrease, so that the brake pressure can be increased again. If this is the case, then the next pressure increase phase can be "programmed" so that the piston 28 now performs a displacement corresponding to the "remainder" of its

  pressure increase stroke possible, or only

  part of this race, depending on the result of

  state of control of the dynamic condition of the wheels of the vehicle.

  It is obvious that we can not

  pel to all possible and favorable regulation algorithms in the direction of an effective anti-blocking regulation, which can be envisaged with correct exploitation of the output signals of the position sensor 92 and the output signals of the rotational speed sensors of the However, the possibilities that exist in principle in this respect have been sufficiently demonstrated by the regulation cycle explained above and consequently it will be possible to dispense with the explanation of other variants corresponding to other

regulation cycles.

  To be complete, however, it is necessary to

  that the intake control valve 37 is

  conducted in its basic position 0 not only when

  the end of one of the anti-blob regulation cycles

  cage or a step of it in which the

  pressure modulator 21 operates in the "failure mode"

  "but it is also reduced to this

  position "inside" an anti-regulation cycle

  blockage - for example in a phase of increasing the pressure thereof - when the driver "relaxes" for a short time the pedal 17 and then acts

  again immediately on the braking apparatus 14.

  This situation is "detected" by the electronic unit

  61 by the fact that, depending on the

  dynamically of the wheels of the vehicle, the regulation must be continued but however the slowdowns of the wheels decrease for a short time because of the brake fluid can return, through the check valves 53 and 54 and through the conduit

  bypass 56, in the tandem master cylinder 14.

  The switching of the intake control valve 37 is advantageous in this case to then restore the brake pressure-to a correct value for the regulation, which would not be possible, at least not in the most favorable way for the regulation, if the admission control valve 37 had been kept closed in the meantime. What has been specified in accordance with

  Figure 1 for the operation control of the

  control valve admission 37 is obviously applicable also for a corresponding control of the valve

bypass 68 of Figure 3.

  By means of the output signals of the position sensor, it is also possible to control a series of important control functions relating to

  the reliability of the ABS system, these operations being

  performed for example during a control cycle that is automatically initiated when switching on.

  ignition or at a time determined by the

  by means of a control switch provided for this purpose. A possible course of such a cycle, which will thus highlight for the specialist the technical means necessary for its realization, will be

  described in the following in relation to the example of

  1: Initially, the ABS control valve 46 is switched to its activation position I, while simultaneously the intake control valve 37 and the brake pressure control valves 51 and 52 occupy their positions. basic positions, and it is maintained

  in this position until a pressure that exists

  was previously in the training pressure chamber

  44 of the pressure modulator 21 is completely canceled and until the piston 28 has reached its left limit position, in Figure 1, associated with the minimum volume of the primary chamber 34. In connection with the output signal of the position sensor 92 which typically defines the position of the piston, and while the other valves 37, 51 and 52 retain

  their basic positions, the return of the com-

  In the basic position, it is triggered that the pressure is increased in the drive pressure chamber 44 of the pressure modulator 21. While the piston 28 is running in the direction of a decrease of the primary chamber 34,

  it occurs as soon as it has reached a pre-

  determined, located between its two limit positions and can be detected by the output signal of the position sensor 92, again a short-term switching

  of the ABS control valve 46 in its operating position

  It is possible to capture this moment of reaction from the temporal correlation with a maximum

  which then occurs for a signal produced during the exci-

  of the ABS control valve 46 by a different

  tiation of the output signal of the position sensor.

  If this reaction time is large enough, it

  is an indication that the valve 46 is difficult to

  to drink and should be controlled. This case of function

  malfunction can be reported optically or acoustically

  to the driver by means of a specific indicator.

  If the reaction time has a permissible value, then the ABS control valve 46 is again switched to its basic position and thus the displacement of the piston is

  continued to the limit position associated with the

  minimal lume of the primary chamber of the pressure modulator

  21. Under the action of the output signal, defining this position, the position sensor 92, again - by switching the control valve-ABS 46 into its activation position I - the return movement of the piston in its other limit position is engaged and the time required for the piston 28 to reach this limit position. If this time interval is too large, it provides a clue that the piston 28

  is a difficult maneuver and this lack of

  may also be reported to the driver by a specific indicator. If the control indicates that the modulator 21 is operating correctly, after the piston 28 has reached its limit position associated with the maximum volume of the primary chamber 34, a switching of the

  intake control valve 37 and control valves

  braking pressure 51 and 52 in their posi-

  closure I and again a return of the valve

  ABS control unit 46 in its basic position 0, that is,

  say the pressure increase position. When this does not produce a displacement of the piston, which can be detected by the fact that the output signal of the position sensor 92 remains constant, this provides a clue that the intake control valve 37 and the valves of

  51 and 52 are sufficient

  watertight - in their closed positions.

  However, if the output signal of the position sensor 92 indicates that the piston 28 is moving, this provides an indication that at least one of the valves 37, 51

  and / or 52 is affected by a leakage. How-

  If this is not the case, the control can be continued by making the intake control valve 37 and the brake pressure regulating valves 51 and 52 separately brought back one after the other. and each for a short time in their basic positions and then switched back to their activation positions, such

  so that the piston 28 performs a displacement each time

  towards its right limit position which is

  associated with the minimum volume of the primary chamber 34.

  From the time correlation of the corresponding control signals with the maxima, occurring in response to a signal obtained by differentiating the output signal of the position sensor, it is again possible to determine the reaction times of these valves. 37, 51 and 52 both for switching in their activation positions I and for their return

in their basic positions 0.

  In a similar way, it is possible

  to determine the reaction times of the valve

  functional command 69 when this valve is provided in

  association with the auxiliary pressure source 48.

  With respect to the control steps which have been described above and which involve the position sensor 92, it is possible to obtain, in the case of the exemplary embodiment of FIG. 3, analogous possibilities of control rather than control. a limited way in that in this case, the valve chamber 76 can not be sealed relative to the braking apparatus 14 and the ball 72 of the valve, when a pressure is established in the primary chamber 34 of the pressure modulator 21 ', is spaced from its seat 71. However, also in the embodiment of Figure 3, one obtains analogous control possibilities when the driver operates - while the vehicle is stopped - l braking system with a force large enough to

  keep the intake valve 37 'closed and to

  thus turn on the control cycle.

  In the following, to explain an advantageous security measure, we will still refer to the

  Figure 1 o has been designated by 101 a valve of

  the arrangement is arranged in the form of a 2/2-way solenoid valve, which is connected between the section, starting from the outlet 39 of the primary chamber 34 of the pressure modulator 21, of the main braking line 41 of the braking circuit. front axle I and its bypass duct 56, which is in direct communication with the

  pressure outlet 38 of the braking apparatus 14.

  This bypass valve 101 is respectively

  at the same time as the inlet valve 37, in

  its basic position 0 represented - the open position

  ture - and in its position of activation I - the closed position - so that also when the inlet valve 37 must remain "hooked" in its closed position, braking can still be performed by

  through the bypass valve 101.

  With reference to FIG. 4, we will now explain with the features of which we will again expressly refer, a variant of the pressure modulators 21 used in the anti-blocking systems.

  Figures 1 and 2, which obviously can be used

  also as the pressure modulator 21 'of the system

anti-lock 10 "of Figure 3.

  As long as elements of the pressure modulator 21 of FIG. 4 are designated by the same numerical references as in FIG.

  will not repeat their description so that the excitement

  of the pressure modulator 21 of Figure 4 will be limited to its differences with the pressure modulator 21 of the

Figure 1.

  In the pressure modulator 21 represented

  4, its piston 28 'is made in two parts, namely the large ring-shaped piston stage 42', which movesably defines the drive pressure chamber 44, and the collar

  piston 32 ', which delimits in a movable manner the primary chamber

  mayor 34. The piston portion 42 'forming the large stage of the piston is provided, on its side directed towards the piston flange 32', with a short guide appendage 102 in the form of a sleeve into which a guide appendage 103 penetrates, of short length in an axial direction and circular cylindrical shape, the piston collar 32 'defining the primary chamber. The two parts 42 'and 32' of the piston 28 'can move slightly relative to each other in the direction of the longitudinal axis.

  central tudinal 24 of the pressure modulator 21.

  Inside a volume 107 in the form of a circular disk, delimited by the extreme end surface 104 of the cylindrical guide appendage 103 of the small piston flange 32 'and the central zone 106

  of the inner frontal surface of the pis-

  your constituent the big piston stage 42 'and its

  In the form of a sheath, there is provided an electronic sensor 108 which produces at its output an electrical signal whose level provides a value of the axial force represented by the arrow 109 and by means of which the small portion 32 'of the piston 28 'is

  repressed against the large part 42 'of the latter.

  This sensor 108, whose output signal thus provides a value of the pressure prevailing in the primary chamber 34 of the pressure modulator 21, has been represented in the simplified representation of FIG. 4 by a circular disk-shaped element, which is maintained between the two parts 42 'and 32' of the piston 28 'and which can, in the volume in the form of a circular disc, be biased as a function of the magnitude of the active force, so as to be more or less compressed (elastically) or deformed in a radial direction, in which case the output signal of this sensor 108 is proportional to the axial compression

  or the corresponding axial deformation.

  Such a pick-up element can be made in a known manner by means of a piezoelectric crystal, for example a quartz plate or by means of a resistant material which is sensitive to

  deformation, or by means of measuring strips of

  longitudinally, which are arranged for example on a plate supported on its periphery and which undergoes, under the influence of the force 109 acting on the small piston neck 32 ', bending with bulge. Sensors 108 of the type defined above produce the output signal proportional to the pressure within a very small strain course, they can be made with spatial dimensions advantageously small and they can therefore, without substantially influencing on the dimensions of the pressure modulator or its piston 28 ', be easily accommodated in the volume 107

  delimited by the parts 42 'and 32' of this piston.

  The output signal of the pressure sensor 108, which typically defines the pressure in the primary chamber 34 of the modulator of

  pressure 21, can be used, if necessary in

  pairing with the output signals of the wheel rotation speed sensors 62 and 63, effectively for control of the pressure decrease phases in the anti-lock control and also for a corresponding pressure adjustment control in the control phases. increase in pressure in the anti-blocking regulation. In operating conditions of

  anti-blocking system 10 - phases of decreasing or increasing pressure - in which the piston 28 'is in a

  position o it does not rest against the additional return spring 96, it is thus relaxed and the output signal of the pressure sensor 108 thus provides a value of the pressure in the primary chamber 34 and also the pressure prevailing in the drive pressure chamber 34 of the pressure modulator 21, these pressures being equal, or at least approximately equal, in this operating condition. Such an operating condition can be detected by means of the output signal, which

  corresponds to it, of the position sensor 92.

  In combination with the output signals of the position sensor 92, it is therefore possible, with the aid of the output signals of the pressure sensor 108, to perform a very fine control of the

anti-lock regulation phases.

Claims (16)

  1. Anti-lock system (ABS) for a vehicle   car having a hydraulic braking system   multiple circuits, which includes at least one cir-   baked closed braking, which is connected to a chamber of   output pressure of a braking device, in the-   what is produced a proportional output pressure   to an actuating force that can be applied   through an inlet valve to a chamber   primary circuit of a pressure modulator, which comprises a pressure outlet to which is connected a bypass duct, terminating at the wheel brake (s), of the static braking circuit, which comprises at least one braking pressure adjustment valve arranged in the form of a 2/2-way solenoid valve, with the aid of which, for controlling the increase, reduction or pressure maintaining phases in the anti-lock regulation, the wheel brake (s) subjected to the regulation may be connected to the output of the primary chamber or may be isolated therefrom, the pressure modulator being   arranged in the form of a piston pump actuated hy-   hydraulically and whose driving pressure chamber   can be connected via a   ABS function control that can be energized   alternatively to the pressure outlet of a hydraulic auxiliary pressure source or its pressure-free storage tank, such that the piston of the pressure modulator, delimiting the primary chamber relative to the driving pressure chamber. , when the inlet valve is open, can be moved under the effect of the pressure of the pressure chamber   drive pressure and in opposition on the one hand to -   the action of a powerful return spring and secondly the pressure in the primary chamber to its limit position associated with a minimum volume of the primary chamber, or, when the drive pressure chamber is connected to the storage tank of the auxiliary pressure source, can be transferred under   the action of the return spring in its other   mite, associated with a maximum volume of the primary chamber, while in addition the maximum increase or reduction of volume of the primary chamber is between 25% and 50% of the volume of the amount of braking liquid can be returned , when operating the device   braking force with the maximum actuation force   in the braking circuit subject to regulation, and furthermore an ABS control unit is provided which produces the control signals necessary for the appropriate control for regulation, the control valve-ABS and the control valves. braking pressure regulation from a processing of the output signals, proportional to the speed of rotation of the wheels and from rotational speed sensors which are associated with the wheels of the vehicle, characterizes that   the inlet valve (37) is arranged in the form of an electro-   switching valve which, in a normal braking operation, that is to say not subject to regulation, occupies its basic position ensuring the connection of the chamber   primary (34) of the pressure modulator (21) with the   pressure portion (38) of the brake apparatus (14) while   that during the periods of decrease and   pressure increase during anti-regulation   blocking, it is controlled by output signals from the electronic control unit (61) of the ABS system (10) so as to move to its activation position (I) where it   insulation of the primary chamber (34) of the   pressure vessel (21) with respect to the pressure output (38) of the braking apparatus (14), while during the duration of the control phases the modulator of   pressure (21) operates in the discharge mode with   Simultaneous operation of the brake pressure regulating valves (51 and 52) of the associated wheel brakes (11 and 12)   the pressure modulator (21) into their   -5, it is returned to its basic position (0).   Anti-blocking system according to claim 1, characterized in that a position sensor is provided   (92), which produces typical output electrical signals   controlling the position of the piston (28) of the pressure modulator   these signals being applied as other information inputs to the electronic control unit (61) of the   ABS system, and in that the control valve for   sion (37) is reduced within a control cycle   anti-blocking action comprising, where appropriate, several phases of reduction, maintenance and re-increase of pressure, in its basic position when the valve   ABS function control (46) is switched to its position   basis, all the brake pressure regulating valves (51 and 52) of the braking circuit subject to regulation occupying their stop positions and the signal   output of the position sensor (92) indicating that the   the modulator (28) has moved to its position   limit corresponding to a minimum volume of the room primary age (34).   An anti-lock system according to claim 1 or claim 2, characterized in that the intake valve (37), after being controlled during an anti-lock control phase to pass through   its stopping position (I) is also reduced to   following in its basic position when, during the regulation, the slowing of the vehicle - which can be detected by the variation of the output signals of the wheel rotation speed sensors - decreases below   a predetermined threshold value.   4. Anti-lock system according to one of the   preceding claims, characterized in that the wheel brake or brakes which are subjected to the anti-lock control are connected, via a check valve (53 or 54), to a bypass duct (56). leading to   the pressure outlet (38) of the braking apparatus (14).   5. Anti-lock system according to any one   Claims 1 to 4, characterized in that the passage   circulation system (98) of the ABS control valve (46) which ensures, in the base position (0) of this valve (46), the connection of the pressure outlet (47) of the auxiliary pressure source (48) with the drive pressure chamber (44) of the pressure modulator (21) is provided with a throttling   (99) limiting the flow velocity of the pres-   to the modulator at a predetermined value.   6. Anti-lock system according to any one   Claims 1 to 5, characterized in that provision is made   another function control valve (69) controllable by output signals from the control electronics unit (61), such that in the base position (0) of said valve a pressure accumulator ( 82), which can be filled by a loading pump (84),   which is maintained at a specific output pressure level   mineral, necessary for the auxiliary pressure source (48), which is controlled by the opening pressure of a pressure limiting valve (92), connected between the pressure outlet (83), the pump (84) and the return conduit (89) terminating at the storage tank (86) is connected via the outlet check valve (88) of the auxiliary pressure source (48) to its pressure outlet ( 47) when the high pressure outlet (83) of the pump (84) is, however, isolated from the   back (88), and that in the first position of   the pressure accumulator (82) is isolated from the pressure outlet (47) of the auxiliary pressure source (48) and the pressure outlet (83) of the pump (84) ) is connected to the conduit   return (86) of the auxiliary pressure source (48).   7. Anti-lock system according to any one   Claims 1 to 6, characterized in that the modu-   pressure vessel (21) is arranged in the form of a stepped profile cylinder having bore stages (26 and 27),   joining each other via a sponge   housing (97), and furthermore a correspondingly stepped profile piston (88), the large diameter stage (42) of which constitutes the moving limit of the drive pressure chamber (44) and whose a small-diameter stage (32) constitutes the moving limit of the primary chamber (34) of the pressure modulator (21), and in that the piston (28) comprises, between its deflasque-shaped zones (32 and 42), applying sealingly against the corresponding bore stage (26 or 27), a central portion decreasing in axial direction and having a conical outer circumferential surface (94) against which   radially supports an actuating rod (93) of the cap-   positioner (92), which has a stroke-to-stroke converter by means of which radial displacements, combined with axial movements of the piston (28) of the actuator rod (93) are converted into signals   which can be processed by means of the electrical unit   control tronic (61) of the ABS system.   8. Anti-lock system according to any one   Claims 1 to 7, characterized in that the spring   return valve (59), urging the modulator piston (28) to its limit position associated with the maximum volume of the chamber   element (34) is in the form of a coil spring of   pressure, which is received over a part of its length cor-   corresponding to the axial dimension of the small stage of the piston, including the conical central part of this piston (28), in   a central blind hole (57) of the piston (28) of the modulator.   9. Anti-lock system according to any one of   Claims 1 to 8, characterized in that the piston (28)   the modulator can be supported by means of a reporting   additional pel (96) against the housing of the pressure modulator (21), the restoring force of this spring reaching its maximum in the position of the piston which corresponds to the minimum volume of the primary chamber (34) and decreasing to the value 0 as the piston (28) deviates from this limit position, within an interval h between about 1/4 and 1/8 of the total stroke H of the piston. 10. Anti-lock system according to claim 9, characterized in that the sum of the maximum values Rlmax and R2max of the restoring forces of the return springs (59 and 96) and the force PBmax 'F2' which is the result of the biasing of the small piston stage (32) by the maximum output pressure PBmax of the brake apparatus (.4), which are directed in the direction of an increase in the volume of the primary chamber, is maximum and is   close to the force PA. F1 who, during a solicitation   of the modulator piston (28) by the outlet pressure PA of the auxiliary pressure source (48), the piston (28) is returned to its limit position associated with the volume minimum of the primary chamber.   11. An anti-blocking system according to one of the claims   9 or 10, characterized in that the other return spring (96) has the form of a annular spring, which is supported on one side against the shoulder (97) of the housing of the pressure modulator.   12. Anti-lock system according to any one   Claims 1 to 11, characterized in that for   each wheel brake (11 and 12) of the brake circuit (I)   may be subject to regulation, a modu-   pressure valve (21), an inlet valve (37), a brake pressure regulating valve (51 or 52)   and an ABS control valve (46) (Figure 2).   13. Anti-lock system according to any one of   Claims 1 to 12, characterized in that between the   pressure portion (38) of the braking apparatus (14) and the portion (41) of the main braking line of the static braking circuit, starting from the pressure output (39) of the primary chamber (34) of the modulator pressure valve (21), there is provided a bypass valve arranged in the form of a 2/2 way solenoid valve (101), which, together with the inlet valve (37), can be switched to the position activation I - the stop position - from   from the open position - the basic position 0.   14. Anti-lock system according to any one of   Claims 1 to 13, characterized in that the piston (28 ')   the modulator is equipped with an electronic sensor for   sion (108), which produces at its output an electrical signal which represents the pressure prevailing in the primary chamber   (34) of the pressure modulator (21).   An anti-lock system according to claim 13, characterized in that the modulator piston (28 ') has a large diameter stage portion (42') and a small diameter stage portion (32 '). ), which is displaceable by translation with respect to the other part, and in that the pressure sensor (108) comprises a   capture element maintained between the two parties   piston and which can be biased in compression or   in pressure of one of the piston portions (32 ') under the   tion of the pressure in the primary chamber (34) of the pressure modulator (21), thus producing at its   output a corresponding electrical signal.   An anti-blocking system according to claim 14, characterized in that the sensing element (108) is arranged in the form of an electrical resistance sensitive to compression or deformation or under   shape of a piezoelectric element.